In terms of the pieces, the current Second Edition of Global 1940 should give you all the categories you’ll need for Anniversary. In fact it’ll give you more than you need because G40 includes unit categories (like tac bombers) and national groups (France and ANZAC) that aren’t part of the Anniversary game. G40 2nd ed includes Italy, for which it provides a full array of nation-specific sculpts; Anniversary has nation-specific Italian troops and tanks, but the rest of the Italian pieces are German or Japanese in design. In G40 1st ed, the only nation-specific Italian sculpt designs were the troops (the tanks were German Panthers in the Italian colour), so the 2nd ed is a better choice. Both Anniversary and G40 also include Chinese units (infantry only), so you’re covered there too.